Hint: Please make sure, that the in-app payment option is allowed in the settings of your app store application.
1. Open the menu drawer in BC 2
2. Hit on the Go Pro bar
3. Choose the option, you are interested in
4. Proceed with the payment in the app store
Please note, that you do not get to download another app either. The pro features are enabled directly in Business Calendar. The Go Pro bar disappears, when the whole pro package is bought and the pro features are unlocked.